1. Field of the Invention
This invention relates to apparatus for detecting shock and more particularly to apparatus for indicating whether a shock of a predetermined magnitude has occurred.
2. Description of the Prior Art
Prior to this invention, there were a wide variety of electronic, mechanical, and electromechanical apparatus to measure shock or acceleration. Most of these devices are large and complex and provide a constant output showing the present value of acceleration. There is a need, however, for small simple devices which can indicate merely whether a shock greater than a particular value has ever occurred. Such devices are useful when used with mechanical or electronic instruments that can be damaged if such a shock is encountered. It is often not possible with these instruments to otherwise determine if the damage has taken place.
One such simple acceleration detector is shown in my U.S. Pat. No. 4,068,613. This patent provides a hollow tube containing a reservoir of liquid and an adjoining plug of gas. If a large enough acceleration occurs, the liquid-gas interfacial barrier is broken which provides visual indication that the acceleration has occurred. However, the only indication that the shock has occurred is a visual one.